Anode and electrolyte for a metal-air battery

ABSTRACT

An anode for an aluminum-air battery may include an anode body, which may contain particles of an aluminum alloy in a sodium matrix. An electrolyte for an aluminum-air battery may consist of one of an aqueous acid and an aqueous lye containing at least one halogen and at least one surfactant.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to German Patent Application No. DE 102014 208 047.9, filed on Apr. 29, 2014, and International PatentApplication No. PCT/EP2015/057742, filed on Apr. 9, 2015, both of whichare hereby incorporated by reference in their entireties.

TECHNICAL FIELD

The present invention relates to an anode for a metal-air battery, inparticular an aluminium-air battery. The invention further relates to anelectrolyte for a metal-air battery, in particular an aluminium-airbattery. The invention additionally relates to a metal-air batteryequipped with at least one such anode and/or with one such electrolyte.

BACKGROUND

Metal-air batteries are usually primary cells, i.e. electricallynon-rechargeable galvanic cells which produce a certain electricalvoltage due to a chemical reaction of the respective metal withatmospheric oxygen. Such a primary cell can also be designated as fuelcell. Unlike primary cells, secondary cells are so-called rechargeablebatteries which can be electrically recharged.

An exemplary structure for a zinc-air battery is known from WO2012/156972 A1.

A zinc electrode for use in a rechargeable battery is known from WO2013/150519 A1.

Known from WO 2013/128445 A1 is a metal-air battery in which spent fuel,namely zinc, is removed with the aid of a liquefier.

It is known from WO2013/150520 A1 for a metal-air battery to flush anelectrolyte with a washing solution to transfer the battery into astandby mode.

It is known from WO 2013/150521 A1 for a metal-air battery to renew anelectrolyte as required.

It is known from WO 2014/009951 A1 to couple a metal-air battery to arechargeable electrical energy storage device, i.e. a rechargeablebattery in such a manner that varying power requirements are met by acorresponding distribution of the power requirement to the metal-airbattery and the respective rechargeable battery. By this means themetal-air battery is buffered with the rechargeable battery and themetal-air battery can be operated in a relatively constant manner sincepower fluctuations can be compensated by the rechargeable battery.

Controls for chargeable batteries are known from DE 11 2010 002 707 T5,from DE 11 2009 000 223 T5, from DE 10 2011 002 549 A1, from DE 10 2013107 033 A1 and from DE 24 17 571 A.

Metal-air batteries can be of great interest for use in electricvehicles since they have a very high chemical energy density. With theaid of these metal-air batteries, the range of an electric vehicle canbe increased significantly compared with rechargeable batteries.

A problem with metal-air batteries is the implementation of a powercontrol which enables a dynamic adaptation, suitable for the vehicle, ofthe electrical energy which can be delivered with the aid of themetal-air battery, to the electrical energy actually required by thevehicle. In vehicles with electric-motor drive, the required electricalenergy is subjected to severe fluctuations which result from the usuallynon-steady-state driving mode. If the metal-air battery is designed fora high power, the lifetime of the battery is reduced even when onlycomparatively little power is required. Accordingly a complex powercontrol is usually required, e.g. combined with a rechargeable batteryas power buffer.

SUMMARY

The present invention is concerned with the problem of providing animproved embodiment for a metal-air battery or for a relevant operatingmethod or for a vehicle equipped therewith which is in particularcharacterized by a high efficiency and/or a high lifetime for thebattery.

This problem is solved according to the invention by the subject mattersof the independent claims. Advantageous embodiments are the subjectmatter of the dependent claims.

According to a first independent aspect of the invention, the anodecomprises an anode body which contains particles of an aluminium alloyin a sodium matrix. Combined with an electrolyte which contains water, aviolent reaction usually takes place on contact of sodium with waterwhich in this case however is stabilized by the aluminium particles.Nevertheless there is a good solubility of the anode or the anode bodyin the respective electrolyte which enables a high electrical power. Theenergy efficiency of the metal-air battery can be improved with theanode proposed according to the invention.

Preferred is an embodiment in which the particles have a particle sizeof 10 μm to 100 μm, preferably of 40 μm to 60 μm. An embodiment in whichthe particles have a particle size of about 50 μm is particularlyadvantageous. As a result of the selected particle size, a comparativelylarge surface is obtained for the aluminium alloy which favours thedesired electrolysis reaction.

In another advantageous embodiment, a fraction of particles in the anodebody can lie in a range of 40% to 80%, preferably of 60% to 70%. Anembodiment in which the fraction of particles in the anode body is about65% is particularly advantageous in this case. The preceding percentagedetails relate to weight percent. The remaining fraction in the anodebody is then formed by the sodium matrix. With a 65% particle fractionthe matrix accordingly has a fraction of 35% in the anode body.

Of particular importance is an embodiment in which the aluminium alloycontains zirconium. By alloying zirconium to aluminium, the formation ofa passive layer on the surface of the anode exposed to the electrolytecan be prevented specifically to such an extent that a formation ofhydrogen is not preferred whereas at the same time a loss due to thetransfer overvoltage is significantly reduced. Electrolysis at the anodesurface results in a passivation of the anode surface which defines atransfer overvoltage. The larger the passive layer, the higher thetransfer overvoltage which is required to penetrate the passive layer.By adding zirconium, the formation of the passive layer can thus bereduced which lowers the transfer overvoltage. It is important that theformation of the passive layer is not completely suppressed by thealloying of zirconium. The absence of the passive layer would have theresult in the case of aluminium that the aluminium decomposes on contactwith water to form hydrogen. However, such strong formation of hydrogenin the electrolyte is undesirable inside the metal-air battery.

According to an advantageous further development, the aluminium alloycan contain 0.01% to 1.00% zirconium, a content of 0.05% to 0.80%zirconium being preferred. A content of about 0.5% zirconium isparticularly advantageous. In particular, the remainder of the aluminiumalloy, apart from the usual unavoidable impurities, is formed byaluminium. Here also the percentage details relate to weight percent.

In order to produce such an anode, in addition a method is proposed inwhich a granular material comprising an aluminium alloy is introducedinto a sodium melt and wherein an anode or an anode body comprising thesodium melt is cast with aluminium granular material introduced therein.In particular, rod-shaped cylindrical anode bodies can thus be achieved.

In addition, it is proposed according to the invention to use a solidcontaining particles of an aluminium alloy in a sodium matrix as anodebody of an anode of a metal-air battery.

According to a second independent aspect of the invention, theelectrolyte for a metal-air battery is formed by an aqueous acid or anaqueous lye containing at least one halogen and at least one surfactant.An aqueous lye is preferred. With the aid of the respective halogen, thechemical reaction at the anode surface can be improved since as a resultof the addition of the halogen, the acid or the lye can better penetratethe passive layer of the respective metal anode. As a result of theaddition of the respective surfactant, the electrochemical reaction canbe improved since the surfactant improves the electron exchange at theanode surface with the electrolyte. Furthermore the surfactant bringsabout an improved dissolution of the gases formed during the reactionwhich also improves the chemical reaction. The electrolyte according tothe invention thus also results in an improvement in the energyefficiency of the metal-air battery.

Advantageously the respective acid or lye comprises a 10% to 40%fraction in water. A 20%±5% acid or lye is preferred. The percentagedetails here again relate to weight percent.

According to an advantageous embodiment, the halogen can comprise a 0.1%to 4.0%, preferably 0.5% to 2% fraction in the acid or lye. Here alsothis involves weight percent. The halogen preferably comprises afluoride, in particular potassium aluminium pentafluoride.

In another embodiment, the acid or lye can contain the surfactant in aconcentration of 0.1% to 2%, preferably in a concentration of 0.2% to1%. Preferably the surfactant is sodium lauryl sulphate.

According to the invention, it is additionally proposed to use acomposition consisting of an aqueous acid or aqueous lye which containsat least one halogen and at least one surfactant as the electrolyte of ametal-air battery, preferably of an aluminium-air battery.

In a first metal-air battery according to the invention which canpreferably be configured as an aluminium-air battery, it is provided toconfigure the at least one anode as the previously described type. In asecond metal-air battery according to the invention which can preferablybe configured as an aluminium-air battery, it is provided to configurethe electrolyte as the previously described type. Preferred here is anembodiment in which the metal-air battery which is preferably configuredas an aluminium-air battery comprises at least one anode of thepreviously described type and an electrolyte of the previously describedtype.

Preferably with regard to its structure, such a metal-air battery isbased on the general idea of arranging a metal anode in a hollowcylindrical cathode which for its part is arranged in a housing of thebattery. An electrolyte space is located radially between anode andcathode. An air space is located radially between cathode and housing.This results in an extremely compact structure for the battery whereby ahigh power density can be achieved.

Furthermore, this structure enables a particularly favourable flowguidance for the electrolyte on the one hand and for the air on theother hand. Thus, an air path leading through the housing is providedwhich leads from an air inlet of the housing, which is connectedfluidically to the air space, to an air outlet of the housing which isconnected fluidically to the air space. An air flow following the airpath and acting on the cathode can thus be produced with the aid of anair supply device. Furthermore an electrolyte path through the housingis provided which leads from an electrolyte inlet of the housing, whichis connected fluidically to the electrolyte space, to an electrolyteoutlet of the housing which is connected fluidically to the electrolytespace. An electrolyte flow following the electrolyte path and acting onthe anode and the cathode can now be generated with the aid of anelectrolyte supply device. As a result of the coaxial arrangement ofhousing, air space, cathode, electrolyte space and anode, low flowresistances can be achieved for the air path and for the electrolytepath so that in particular large volume flows for the air along the airpath on the one hand and for the electrolyte along the electrolyte pathon the other hand can be achieved. Consequently sufficient oxygen can besupplied subsequently to the cathode particularly simply. In addition,sufficient unused electrolyte can be supplied subsequently to the anodeor spent electrolyte can be removed. In the present connection “action”of a fluid on a body can be understood as contact of the body beingacted upon by the respective fluid regardless of whether the fluid issupplied by means of positive pressure or extracted by means of negativepressure.

Furthermore, it is in particular possible to configure the air supplydevice so that the volume flow of air along the air path is adjustablein a relatively large range, i.e. is variable. Likewise the electrolytesupply device can be simply configured so that the volume flow ofelectrolyte is adjustable in a relatively large range, i.e. is variable.In this way, the electrical power which can be tapped at the metal-airbattery can be adjusted particularly simply hydraulically by varying theelectrolyte flow and/or pneumatically by varying the air flow.

According to a preferred embodiment, the metal-air battery is configuredas an aluminium-air battery so that the anode has an anode body exposedto the electrolyte which comprises an aluminium alloy or consiststhereof.

According to an advantageous embodiment, a control device can beprovided for operation of the metal-air battery which on the one hand iselectrically connected to the air supply device and on the other hand tothe electrolyte supply device. The control device can now be configuredor programmed so that depending on a current electrical powerrequirement at the metal-air battery, it actuates the air supply deviceto produce an air flow adapted to this power requirement and/or actuatesthe electrolyte supply device to produce an electrolyte flow adapted tothis power requirement. By varying the volume flow of electrolyte and/orair, the electrical power which can be tapped at the metal-air batterycan be varied. Since the volume flows of air and/or electrolyte can bevaried comparatively simply and comparatively rapidly within arelatively large range, the electrical power which can be tapped at themetal-air battery can be adapted relatively rapidly to the currentlyrequired power by means of the procedure presented here. In particular,the provided power which can be tapped at the metal-air battery can beadapted in a short time to low power requirements by reducing the airflow and/or electrolyte flow whereby the lifetime of the metal-airbattery can be significantly lengthened. The power control or powerregulation presented here operates hydraulically or hydropneumatically.

In particular, the control device can achieve a power control where ittakes account of the current power requirement as the desired value andtakes account of an electrical power measured currently at electrical orgalvanic power connections of the metal-air battery as the actual value.By means of a desired-actual value comparison, the control device cantrack the volume flow for the electrolyte and/or for the airaccordingly.

According to another advantageous further development, the controldevice can be configured or programmed so that depending on the currentpower requirement it actuates the electrolyte supply device to producethe electrolyte flow adapted to this power requirement and actuates theair supply device to produce an air flow adapted to the adaptedelectrolyte flow. In other words, the control device initiallydetermines in a first step the volume flow of electrolyte required forthe current power requirement and actuates the electrolyte supply deviceaccordingly. In a second step which can take place quasi-simultaneouslyto the aforesaid first step, the control device determines depending onthe determined electrolyte volume flow an air volume flow required forthis and actuates the air supply device accordingly.

In another advantageous further development, it can be provided that thecontrol device is configured or programmed so that it actuates theelectrolyte supply device for emptying the electrolyte path ofelectrolyte for shutting down the metal-air battery. As a result of suchemptying of the electrolyte path, in particular the electrolyte space,the chemical reaction between anode and electrode in the metal-airbattery is completely interrupted whereby the decomposition ordissolution of the anode is severely reduced. Accordingly the lifetimeof the battery is lengthened.

In another advantageous embodiment, the anode can be rotatably mountedabout its longitudinal central axis on the housing. As a result of thetwistability of the anode relative to the housing, a rotation of theanode relative to the vertical housing can be achieved. The anodethereby also rotates relative to the cathode which is torque-proofrelative to the housing. The rotating anode improves the flow ofelectrolyte around the anode. At the same time, reaction products can bebetter released from the anode as a result of centrifugal forces, whichincreases the surface area of the anode available for electrolysis.

If the anode is arranged rotatably in the housing, a correspondingrotary drive, for example, by an electric motor, can fundamentally beprovided in order to set the anode in rotation. Alternatively it can beprovided that the anode is configured so that a rotation of the anodedrives the electrolyte in the electrolyte path. By this means the anodeacquires an additional function. Particularly advantageous here is afurther development in which the anode has flow guiding structures onits outer side exposed to the electrolyte space which drive theelectrolyte when the anode is rotating. In particular, rotor bladesarranged in a screw shape are feasible.

According to another embodiment, it can be provided that the anode isdriven by the electrolyte flow i.e. hydraulically. For this purpose, theelectrolyte is guided past the anode so that the electrolyte flowrotatingly drives the anode. Thus, the kinetic energy of the electrolyteflow is used to set the anode in rotation. An additional,energy-consuming electric drive can thus be dispensed with.

According to an advantageous further development, the electrolyte inletcan be arranged tangentially to the electrolyte space at a first endregion of the electrolyte space whilst the electrolyte outlet isarranged at a second end region of the electrolyte space, in particularaxially. As a result of the spaced-apart arrangement of electrolyteinlet and electrolyte outlet, a quasi-axial through-flow of theelectrolyte space is achieved for the electrolyte. As a result of thetangential arrangement of the electrolyte inlet, a screw-shapedthrough-flow is obtained in the electrolyte space which can also bedesignated as swirling flow. As a result of surface friction, theswirling flow results in a rotational movement of the anode. Thetangential arrangement can be found in a cross-section of the air spaceor of the cathode which runs perpendicular to the longitudinal centralaxis of the cathode.

Additionally or alternatively, the anode can have flow-guidingstructures on its outer side exposed to the electrolyte space whichtransmit a torque to the anode when the anode is exposed to theelectrolyte flow. Thus, kinetic energy of the electrolyte flow can beused to drive the anode.

The rotation of the anode can be accomplished by a corresponding volumeflow of the electrolyte with a comparatively high rotational speed whichin particular can be selected to be so high that sufficient centrifugalforces are produced to enable a release of reaction products from theanode. Rotational speeds of up to 300 revolutions per minute arefeasible, for example.

The housing is expediently insulated or made from an electricallyinsulated material, for example, of plastic. The arrangement of theanode in the housing is advantageously accomplished so that thelongitudinal central axis of the anode and therefore also a longitudinalcentral axis of the cathode extend substantially vertically in the usagestate of the battery.

According to another advantageous embodiment, the anode or an anode bodycan be configured cylindrically and connected mechanically andelectrically to a metal supporting plate. This design enables the anodeto be positioned more simply in the housing, e.g. coaxially in thecathode.

According to an advantageous embodiment, the in particular circularsupporting plate can be mounted rotatably about a longitudinal centralaxis of the anode by means of an axial bearing on the housing. Thus, theanode is mounted rotatably on the housing in the region of itssupporting plate. The supporting plate can be made of a different metalto the anode, whereby the formation of a suitable mounting in the regionof the supporting plate is simplified. By means of the axial bearing,axial forces can be supported particularly simply between the anode andthe housing. The axial bearing can be arranged, for example, on an axialface of the housing which is arranged at the top in the operating stateof the battery.

In another further development, an anode-side galvanic power connectionof the metal-air battery which represents an electrical negative polecan be formed on the axial bearing. The axial bearing has a regionfirmly connected to the housing which can also be designated asstationary region and which is particularly suitable for the formationof an anode-side power connection. As a result, the said anode-sidepower connection is stationary although the anode itself is rotatablerelative to the housing. The current collection at the battery isthereby simplified.

According to another further development, the axial bearing can beconfigured as a plain bearing and comprise a sliding metal ring whichlies in a housing-side annular bearing shell and on which the supportingplate rests and on which the supporting plate slides when the anoderotates. As a result of the configuration of the axial bearing as aplain bearing, a comparatively large contact area can be achievedbetween supporting plate and axial bearing or sliding metal ring, whichsimplifies the power transmission between anode and axial bearing.

An embodiment is particularly advantageous in which the sliding metalring comprises an annular body made of a sliding metal alloy and atleast one preferably metal heating conductor arranged in the annularbody by means of which the annular body can be heated. The heating ofthe annular body can improve the power transmission between slidingmetal ring and supporting plate.

A further development is particularly advantageous in which a powersupply of the heating conductor is configured so that the heatingconductor heats the annular body to a predetermined operatingtemperature which lies below a melting point of the sliding metal alloyand at the same time lies so close to the melting point of the slidingmetal alloy that a surface melting occurs on the annular body. Thesliding metal alloy here is a low-melting alloy whose melting point can,for example, lie between 50° C. and 300° C. The predetermined operatingtemperature lies for example 10% to 15% below the melting point, inparticular about 40° C. below the melting point. As a result of thesurface melting thus brought about, a liquid metal film is formed on thesurface of the sliding metal ring on which the supporting plate slidesin the manner of a hydro bearing. On the one hand, the friction betweensupporting plate and sliding metal ring is thereby significantlyreduced. On the other hand a significantly improved electrical contactis achieved as a result of the liquid metal film. For example, aformation of an oxide layer of the surfaces in contact with one anothercan be reduced in the liquid metal film. As a result of theconfiguration presented here, an extremely low-loss electrical contactcan be achieved between supporting plate and axial bearing whereby highcurrents can be achieved at low voltages.

The control of the power supply of the heating conductor with the aid ofwhich the desired operating temperature can be adjusted in the annularbody can be accomplished, for example, by means of a temperaturemeasurement. It is also feasible to connect the respective heatingconductor in series with a PTC element where PTC stands for positivetemperature coefficient. The respective PTC element is tuned to thedesired operating temperature. In this way, a self-regulating heating ofthe respective heating conductor can be provided without majorelectronic expenditure by which means the annular body can bespecifically heated to the predetermined operating temperature.

The power supply of the respective heating conductor can expediently beincorporated into the current path between the anode and the anode-sidegalvanic power connection.

In another advantageous embodiment, the air supply device can have aconcentrating device upstream of the air inlet which increases theoxygen fraction in the air flow. Thus, an enrichment of the air flowwith regard to the entrained oxygen is accomplished which accordinglyimproves the electrolysis function at the cathode. Such a concentratingdevice can, for example, be equipped with a corresponding filtermembrane or a corresponding molecular sieve whereby on one side thenitrogen fraction increases and the oxygen fraction decreases whilst onthe other side the nitrogen fraction decreases and the oxygen fractionincreases. For example, with the aid of such a concentrating device thenatural oxygen content can be increased from about 20% in air to over90%.

If a filter medium which must be periodically regenerated is used here,the concentrating device comprises two or more concentrating units sothat an increase in the oxygen fraction by means of at least oneconcentrating unit can be carried out permanently whilst at the sametime another concentrating unit is regenerated.

In another advantageous embodiment, the electrolyte supply device canhave an electrolyte circuit which comprises a flow and a return. Theflow leads from an electrolyte tank to the electrolyte inlet whilst thereturn leads from the electrolyte outlet to the electrolyte tank. Byusing such a closed electrolyte circuit, the electrolyte can be usedpermanently. In particular, higher volume flows for the electrolyte arethereby possible which are so high that the electrolyte is notcompletely unusable during flow through the electrolyte path.

According to an advantageous further development, a flow pump fordriving the electrolyte is arranged in the flow, For example, thecurrent volume flow of electrolyte which is guided through theelectrolyte path can be adjusted by means of the flow pump.

In another embodiment, a return pump for driving the electrolyte can bearranged in the return. The return pump is used to convey theelectrolyte from the electrolyte outlet to the electrolyte tank. It canbe used in particular for emptying the electrolyte space or theelectrolyte path, e.g. in conjunction with a controllable ventilationand aeration of the electrolyte circuit.

In another embodiment, an electrolyte cleaning device for removingreaction products from the electrolyte can be arranged in the return.Such an electrolyte cleaning device is expediently located downstream ofthe return pump and can, for example, be configured as a centrifuge withmembrane. With the aid of the electrolyte cleaning device, theelectrolyte coming from the electrolyte space can be prepared in such amanner that the prepared electrolyte can again be supplied to theelectrolyte space. The consumption of electrolyte is minimized by thismeans.

In another advantageous embodiment, a gas separating device can bearranged in the return for removing gases from the liquid electrolyte.Gases, in particular hydrogen, can be formed in the electrolysisreaction in the metal-air battery. The gases should be separated fromthe liquid electrolyte, for example, in order to improve the efficiencyof the electrolysis function. In particular any formation of foam in theelectrolyte should also be avoided. The gas separating device can, forexample, operate with nozzles whereby particularly large gas bubbles areformed in the electrolyte which can be separated relatively easily.

According to an advantageous further development, the gas separatingdevice can be fluidically connected via a gas line to a conversiondevice for converting the chemical energy of the separated gases intoelectrical and/or thermal energy. Thus, the chemical energy of the gasaccumulating as waste product can be used to improve the entire energyefficiency of the metal-air battery.

According to an advantageous further development, the conversion devicecan be a catalytic burner which for example comprises a platinum mesh.The gaseous hydrogen is reacted with atmospheric oxygen to form water.The heat formed can be used for heating the battery. Alternatively tothis, the conversion device can be formed by a hydrogen-air fuel cell inwhich the hydrogen gas is reacted with oxygen gas to form electricalcurrent and heat. The heat can again be used for heating the battery.The electrical energy can also be used inside the battery or asadditional electrical power. A suitable hydrogen-air fuel cell can beconfigured as a low-temperature fuel cell or PEM fuel cell where PEMstands for proton exchange membrane. In principle, an embodiment as ahigh-temperature fuel cell, in particular as a SOFC fuel cell, whereSOFC stands for solid oxide fuel cell, is also feasible.

The heat transfer between the conversion device and the remainingmetal-air battery can be accomplished, for example, with the aid of aheat transfer agent which is incorporated in the electrolyte circuit ina suitable manner. Also excess heat can be withdrawn from theelectrolyte using this heat transfer agent. The heat can then bespecifically used to heat the anode and/or the cathode to improve theelectrolysis reaction.

In another advantageous embodiment, the air inlet can be arrangedtangentially to the air space. Additionally or alternatively the airoutlet can be arranged tangentially to the air space. The tangentialarrangement of the air inlet or the air outlet can be used to configurethe air flow inside the air space as screw-shaped, i.e. as swirlingflow, with the result that an increased dwell time for the air flowinside the air space is achieved. This improves the transfer of oxygenbetween air flow and cathode.

According to another advantageous embodiment, an induction heating canbe provided to heat the anode. Such induction heating operates, forexample, with at least one induction coil which produces a stationary,spatially inhomogeneous electromagnetic field in the region of theanode. By moving or rotating the anode in this electromagnetic field,heat is induced in the anode, in particular in a wall region facing theelectrolyte space which significantly improves the electrolysisreaction.

The respective induction heating can be arranged in the region of thecathode with the result that a particularly compact design can beachieved. The anode can be heated with the aid of induction heating andspecifically in the wall region facing the electrolyte space. By thismeans only comparatively little energy is required to heat the actualreaction zone. The increased temperature in the reaction zone improvesthe energy efficiency of the metal-air battery.

A battery system can comprises a plurality of metal-air batteries of thepreviously described type and is characterized by a common air supplydevice for producing the respective air flow through the air paths ofthe batteries and/or by a common electrolyte supply device for producingthe respective electrolyte flow through the electrolyte paths of thebatteries and/or by a common control device for operating the batteries.The batteries can be fluidically connected in series or in parallel withtheir air paths and/or with their electrolyte paths. This designsimplifies the implementation of a high-performance battery system. Inparticular, a common air conveying device can be used for a plurality ofbatteries. Additionally or alternatively an electrolyte conveying devicecan be used for a plurality of batteries. Additionally or alternativelythe control or regulation of the battery system is also simplified sincea common control device can be used for a plurality of batteries.

A vehicle which can preferably comprise a road vehicle can have anelectric motor drive and can be fitted with at least one metal-airbattery of the previously described type. The vehicle is characterizedin particular by a power electronics for the power supply of theelectric drive which is coupled unbuffered to the respective metal-airbattery. An electrically unbuffered coupling corresponds to a directelectrical connection which is made without an interposed electricalenergy storage device, i.e. in particular without an interposedrechargeable battery. The invention is therefore based with regard tothe vehicle on the general idea to use the respective metal-air batterydirectly for the power supply of the electric drive so that theinterposition of an additional electrical energy storage device such as,for example a rechargeable battery can be dispensed with.

A method for operating such a battery can be based on the general ideaof hydraulically or pneumatically controlling or regulating theelectrical power output of the metal-air battery. In other words, thepower control or power regulation of the metal-air battery isaccomplished by means of a specific variation of the volume flows of theelectrolyte and/or the air. Such a pneumatic or hydraulic powerregulation or control can be achieved particularly simply withconventional components such as, for example, fans and/or pumps.

Accordingly it can be provided according to an advantageous embodimentthat at least one electrolyte conveying device, e.g. a suitable pump, isactuated accordingly to increase or reduce its conveying capacity foradaptation of the electrolyte flow. Additionally or alternatively it canbe provided that at least one air conveying device, e.g. a suitable fanis actuated accordingly to increase or reduce its conveying capacity foradaptation of the air flow.

Further important features and advantages of the invention are obtainedfrom the subclaims, from the drawings and from the relevant descriptionof the figures by reference to the drawings.

It is understood that the aforesaid features and those to be explainedhereinafter can be used not only in the respectively specifiedcombination but also in other combinations or alone without departingfrom the framework of the present invention.

Preferred exemplary embodiments of the invention are shown in thedrawings and are explained in detail in the following description wherethe same reference numbers refer to the same or similar or functionallythe same components.

BRIEF DESCRIPTION OF THE DRAWINGS

In the figures, in each case schematically,

FIG. 1 shows a highly simplified circuit-diagram-like schematic diagramof a metal-air battery without peripheral components,

FIG. 2 shows a view as in FIG. 1 but with peripheral components.

DETAILED DESCRIPTION

According to FIGS. 1 and 2, a metal-air battery 1 which preferablycomprises an aluminium-air battery comprises a housing 2 which iselectrically insulated and preferably consists of an electricallyinsulating material, for example, of plastic. In the example shown, thehousing 2 is configured as a cylindrical container and has a cylindricaljacket 3 as well as a plate-shaped, in particular circular base 4. Inthe installed state or ready-to-use state of the metal-air battery 1which is hereinafter designated for short as battery 1, the housing 2 isarranged so that a longitudinal central axis 5 of the housing 2 isaligned substantially vertically, i.e. substantially parallel to thedirection of gravity 6, which is indicated by an arrow in FIG. 1. Thebattery 1 further comprises at least one hollow-cylindrical cathode 7which is disposed in the housing 2 and specifically preferably so thatin the ready-to-use state of the battery 1, a longitudinal central axis8 of the cathode 7 runs substantially parallel to the direction ofgravity 6. In the example shown the housing 2 and the cathode 7 arearranged coaxially and concentrically with respect to one another sothat the two longitudinal central axes 5, 8 coincide. The cathode 7separates an air space 9 from an electrolyte space 10 in the housing 2.

The cathode 7 usually consists of a porous material whereby a largesurface area is made available to the usually liquid electrolyte whichenables contact with the gaseous oxygen contained in the air. Forexample, the cathode can be formed from a permeable membrane or comprisesuch a membrane.

Furthermore the battery 1 comprises at least one metal anode 11 which isarranged in the electrolyte space 10. The anode 11 possesses for examplea cylindrical anode body 12 with a longitudinal central axis 13 and isarranged coaxially to the cathode 7 and in particular concentricallythereto. Accordingly the longitudinal central axes 5, 8, 13 coincidehere.

An air path 14 leads through the housing 2, which air path is indicatedby arrows in FIG. 1 and which fluidically connects an air inlet 15 ofthe housing 2 inside the housing 2 through the air space 9 to an airoutlet 16 of the housing. In addition, an electrolyte path 17 leadsthrough the housing 2, which electrolyte path is indicated by arrows inFIG. 1 and which fluidically connects an electrolyte inlet 18 of thehousing 2 through the electrolyte space 10 to an electrolyte outlet 19of the housing 2.

The battery 1 is additionally fitted with an air supply device 20 withthe aid of which an air flow can be generated for operation of thebattery 1 which during operation of the battery 1 follows the air path14 and thereby acts upon the cathode 7, i.e., flows against it or flowsaround it. In addition, an electrolyte supply device 21 is provided withthe aid of which an electrolyte flow can be generated for operation ofthe battery 1 which during operation of the battery 1 follows theelectrolyte path 17 and thereby acts upon the anode 11 on the one handand on the cathode 7 on the other hand, i.e., flows against it or flowsaround it.

For operation of the battery 1 according to FIG. 2 a control device 22is provided, for example, in the form of a controller. The controldevice 22 is electrically connected to the air supply device 20 and tothe electrolyte supply device 21, for example via corresponding controldevices 23. The control device 22 can in addition be electricallyconnected via corresponding signal lines 24 to a sensor system of thebattery 1 not shown in detail here. If the battery 1 is used in asuperordinate system, in particular in a vehicle, for provision ofelectrical energy, the control device 22 is additionally connected viasuch a control line 24 to a control of the system or the vehicle notshown here so that the control device 22 knows the current electricalpower requirement of the system or the vehicle. This current powerrequirement corresponds in this case to a current power requirement tothe battery 1.

The control device 22 is now configured or programmed so that itactuates the air supply device 20 and/or the electrolyte supply device21 depending on the current electrical power requirement at the battery1 in such a manner that the air supply device 20 generates an air flowadapted to the current power requirement and/or the electrolyte supplydevice generates an electrolyte flow adapted to the current powerrequirement. Preferably the configuration or programming of the controldevice 22 is accomplished in such a manner that depending on the currentpower requirement it initially determines in a first step a suitableelectrolyte flow, for example, by means of characteristic lines orcharacteristic areas or by means of suitable calculation formulae andthen actuates the electrolyte supply device 21 in such a manner thatthis generates the determined electrolyte flow. In a second step, whichcan take place quasi parallel, the control device 22 can determine anair flow required for the determined electrolyte flow, likewise by meansof characteristic lines or characteristic areas or by means of suitablecalculation formulae so that it can then actuate the air supply device20 to generate the determined air flow.

The control device 22 therefore enables a hydraulic or hydropneumaticpower control or power regulation of the battery 1. If the powerrequirement increases, the volume flows for electrolyte and air areincreased accordingly. If the power requirement is reduced on the otherhand, the volume flows for electrolyte and air are reduced accordingly.Thus, the wear of the battery 1, i.e. the dissolution of the anode 11,is minimized. The battery 1 as a result has a comparatively longlifetime.

The control device 22 can additionally be programmed or configured sothat for example for shutting down the battery 1 it actuates theelectrolyte supply device 21 so that it empties the electrolyte space 10or the entire electrolyte path 17 of electrolyte. This can additionallybe followed by a flushing with a corresponding neutral or inert flushingmedium.

As can be deduced in particular from FIG. 1, the anode 11 according to apreferred embodiment can be mounted rotatably about its longitudinalcentral axis 13 on the housing 2. A corresponding rotary movement isindicated by a rotary arrow 25 in the figures. As a result of the rotarymovement of the anode 11, the contact between anode 11 and electrolyteis improved, which improves the electrolytic reaction to the currentgeneration. At the same time, the rotation of the anode 11 atcorresponding rotational speeds can produce centrifugal forces which canbring about a release of reaction products from the anode 11 which alsoimproves the efficiency of the electrolyte reaction. The anode 11 or itsanode body 12 is arranged on a metal supporting plate 26 and ismechanically and electrically connected to this. In this respect, thesupporting plate 26 can also be counted as the circumference of theanode 11. The supporting plate 26 is mounted rotatably about thelongitudinal central axis 13 of the anode 11 by means of an axialbearing 27 on the housing 2. To this end, the axial bearing 27 isarranged on a face 28 of the housing jacket 3 facing away from the base4.

The battery 1 possesses two galvanic or electrical power connections 29,30, namely a first electrical power connection 29 which represents anegative pole connected electrically to the anode 11 and a secondelectrical power connection 30 which represents a positive poleconnected electrically to the cathode 7.

In the preferred example shown here, the anode-side galvanic powerconnection 29 is formed on the axial bearing 27 and firmly connectedthereto, with the result that it is fixed in relation to the housing 2and unlike the non-stationary or rotating anode 11, is arranged in astationary or torque-proof manner.

The axial bearing 27 can fundamentally be configured as a rollerbearing. Preferred however is the embodiment shown here in which theaxial bearing 27 is configured as a plain bearing. In particular, theaxial bearing 27 can to this end comprise a sliding metal ring 31 and anannular bearing shell 32. The bearing shell 32 is firmly arranged on thehousing 2. The sliding metal ring 31 is inserted in the bearing shell32. To this end the bearing shell 32 in the example has an axially openannular groove 33. The sliding metal ring 31 lies in the annular groove33. The supporting plate 26 rests on the sliding metal ring 31 andduring operation of the battery 1 can slide thereon. The sliding metalring 31 has an annular body 34 which consists of a sliding metal alloyand at least one metal heating conductor 35 which is arranged in theannular body 34. The annular body 34 can be heated with the aid of theheating conductor 35. A power supply of the heating conductor 35 notshown here can be configured so that the heating conductor 35 heats theannular body 34 to a predetermined operating temperature which on theone hand lies below a melting point of the sliding metal alloy and whichon the other hand lies so close to the melting point of the slidingmetal alloy that a surface melting occurs on the annular body 34. Forexample, the operating temperature is about 10% to 20% below the meltingpoint of the sliding metal alloy. A low-melting alloy is expedientlyused as sliding metal alloy which has a maximum melting point of 250° C.to 350° C. The heating of the annular body 34 to the predeterminedoperating temperature results in the said surface melting at the annularbody 34 so that an external surface of the annular body 34 liquefies atleast in the region of the supporting plate 26. On the one hand, thisresults in an extremely low-friction hydraulic plain bearing. On theother hand, the electrical contact between sliding metal ring 31 andsupporting plate 26 is thereby improved significantly with the resultthat large currents can be transferred at low voltages.

The aforesaid power supply of the heating conductor 35 can beimplemented by a separate power supply which can be controlled orregulated with the aid of the control device 22, e.g. in conjunctionwith a temperature sensor in order to adjust the desired operatingtemperature at the annular body 34. In a simplified case the powersupply can be implemented with the aid of at least one PTC element whichis connected in series with the heating conductor 35 at a suitablepoint. It is feasible in particular to introduce the heating conductor35 in parallel into a flow path between the supporting plate 26 and theaxial bearing 32, possibly including the respective PTC element.

According to another advantageous embodiment which is also shown here,the electrolyte path 17 is guided past the anode 11 or the anode body 12so that the electrolyte flow during operation of the battery 1rotatingly drives the rotatably mounted anode 11. To this end theelectrolyte inlet 18 can be arranged tangentially to the electrolytespace 10. Accordingly the inflow of electrolyte into the electrolytespace 17 takes place close to the cathode 7. Furthermore it can beprovided that the electrolyte inlet 18 is arranged on a first end regionof the electrolyte space 10, here distally to the base 4 or in theinstalled state at the top whereas the electrolyte outlet 19 is arrangedon a second end region of the electrolyte space 10 which is remote fromthe first end region. In the example of FIG. 1 or in the installedstate, the electrolyte outlet 19 is located proximally to the base 4,i.e. at the bottom. In the example shown the electrolyte outlet 19 is inaddition axially oriented and guided through the base 4. The arrangementof electrolyte inlet 18 and electrolyte outlet 19 at opposite axial endsof the electrolyte space 10 brings about an axial flow of electrolytethrough the electrolyte space 10. The tangential arrangement of theelectrolyte inlet 18 produces a swirling flow or screw-shaped flow inthe electrolyte space 10 which rotatingly drives the anode 11 as aresult of friction effects. However, the swirling flow in theelectrolyte space 10 also enables comparatively high flow velocitieswith a comparatively high dwell time for the electrolyte in theelectrolyte space 10.

In the example, the anode 11 or the anode body 12 is formed on an outerside 36 with flow-guiding structures 37 exposed to the electrolyte space10. The flow-guiding structures 37 are configured in such a manner thatthey can transmit a torque to the anode 11 when the anode 11 is actedupon by an electrolyte flow. The flow-guiding structures 37 cantherefore utilise kinetic energy of the electrolyte flow for driving theanode 11. The flow-guiding structures 37 can, for example, be formed byscrew-shaped vanes or vane sections. The flow-guiding structures 37 arehere provided cumulatively to the tangential electrolyte inlet 18 butcan also be provided alternatively thereto.

Whereas in the previously described example, the electrolyte flow whichis generated in a suitable manner is used to rotatingly drive the anode11, according to another embodiment it can be provided to use therotation of the anode 11 for driving the electrolyte, i.e. for producingthe electrolyte flow. To this end, a rotary drive 56 indicated by theinterrupted line in FIG. 2 can be provided which rotatingly drives theanode 11. In the example, the rotary drive 56 which for example can bean electric motor, drives the supporting plate 26 which carries theanode body 12. In this case, the flow-guiding structures 37 operate likerotor blades of an axial flow machine such as, for example a propeller.The driven anode 11 in this case forms an electrolyte conveying device.The control device 22 can be electrically connected to a rotary drive 56via a corresponding control line 23 in order to be able to actuate therotary drive 56 as required.

According to FIG. 2, the air supply device 20 has a concentrating device38 upstream of the air inlet 15 with the aid of which the oxygenfraction in the air flow can be increased. The concentrating device 38can in this case operate by means of suitable filter structures, inparticular membranes and the like. Accordingly the air flow downstreamof the concentrating device 38 has a significantly increased oxygenfraction compared to the air flow upstream of the concentrating device38. An air flow with correspondingly reduced oxygen fraction orincreased nitrogen fraction can be removed from the concentrating device38 via an exhaust air line 39. The air supply device 20 hereadditionally possesses a fan 40 for driving or for producing the airflow. The fan 40 can be actuated by the control device 22. In addition,a “normal” air filter not shown here can be contained in the air supplydevice 20 by means of which liquid and/or solid impurities can befiltered out from the air.

According to FIG. 2 the electrolyte supply device 21 is fitted with aclosed electrolyte cycle 41 which comprises a flow 42 and a return 43.The flow 42 connects an electrolyte tank 44 for providing theelectrolyte fluidically to the electrolyte inlet 18. A flow pump 45 islocated in the flow 42 which can be actuated with the aid of the controldevice 22. The return 43 connects the electrolyte outlet 19 fluidicallyto the electrolyte tank 44 and contains a return pump 46 which can beactuated with the aid of the control device 22. The flow pump 45 andreturn pump 46 here form electrolyte conveying devices.

In addition, an electrolyte cleaning device 47 is located downstream ofthe return pump 46 in the return 43, with the aid of which reactionproducts can be removed from the electrolyte. Thus, preparation of theelectrolyte takes place inside the electrolyte cleaning device 47 sothat cleaned or non-spent electrolyte can be supplied to the electrolytetank 44. The electrolyte cleaning device 47 can, for example, beconfigured as a centrifuge, in particular with a membrane, Thecentrifuge can be configured as a back jet centrifuge which is driven bythe kinetic energy of the electrolyte flow.

In addition, a gas separating device 48 can be arranged in the return 43with the aid of which gases can be separated from the liquidelectrolyte. In the example, the gas separating device 48 is locateddownstream of the return pump 46 or downstream of the electrolytecleaning device 47. The separated gas comprises in particular hydrogengas formed during the electrolyte reaction in the electrolyte space 10.For improved gas separation the gas separating device 48 can contain aplurality of nozzles by means of which the liquid electrolyte can bepressed through. It has been shown that the nozzles intensify bubbleformation which simplifies the separation of gas from the liquidelectrolyte.

The gas separating device 48 is fluidically connected via a gas line 49to a conversion device 50 with the aid of which the chemical energy ofthe separated gas can be converted into electrical and/or thermalenergy. For example, the conversion device 50 comprises a catalyticburner so that the combustible gases are converted exothermally toproduce heat. Alternatively the conversion device 50 can comprise ahydrogen-air fuel cell which converts separated hydrogen gas with theaid of atmospheric oxygen into heat and electrical energy. The energyconverted with the aid of the conversion device 50 from the separatedgases can be supplied according to an arrow 51 to the battery 1 or therespective superordinate system i.e. in particular to the vehicle.

Furthermore a heat exchanger 55 can be located in the return 43 with theaid of which the returned electrolyte can be cooled. The heat therebydissipated can either be supplied to the reaction zone inside theelectrolyte space 10 or to the superordinate system to the battery 1, inparticular the vehicle. In the example of FIG. 2 the heat exchanger 55is integrated in the gas separating device 48.

According to FIG. 1, in order to increase a dwell time of the air flowinside the air space 9, it can be provided to arrange at least the airinlet 15 tangentially to the air space 9. Furthermore air inlet 15 andair outlet 16 are arranged at ends of the air space 9 remote from oneanother. A converse arrangement compared with the electrolyte path 17 ispreferred here so that the so-called counter-flow principle can beimplemented for the electrolyte path 17 and the air path 14.Accordingly, in the example the air inlet 15 is located proximally tothe base 4 whilst the air outlet 16 is located distally to the base 4.

An induction heating 52 can be provided for heating the anode 11 or theanode body 12, which in the example is located in the area of thecathode 7. With the aid of the induction heating 52 the anode 11 or theanode body 12 can on the one hand be heated in a non-contact manner. Onthe other hand the heating takes place specifically in the area of theouter side 36 facing the electrolyte space 10, which is also exposed tothe electrolyte flow. Consequently, the heating takes place specificallywhere an increased temperature is desired for an improved electrolytereaction. The induction heating 52 is in particular configured so that avertical electromagnetic field is generated with alternating magneticpolarization in the circumferential direction, which only takes placewith a relative movement of the anode 11 for the desired surface heatingof the anode 11 or the anode body 12 due to induction. The relativemovement of the anode 11 is accomplished by rotation of the anode 11about its longitudinal central axis 13. The inductive heating isspeed-controlled where the rotational speed of the anode 11 depends onthe volume flow of the electrolyte.

Although in the preferred example shown here only a single cathode 7 andonly a single anode 11 are arranged in the housing 2, in anotherembodiment it can be provided to arrange a plurality of cathodes 7 and aplurality of anodes 11 in the same housing 2. It is also feasible toarrange a plurality of anodes 11 in the same cathode 7.

A battery system designated globally with 57 in FIG. 2 comprises atleast two metal-air batteries 1 of the previously described type wherehowever the peripheral aggregates or components can be used jointly. Forexample, a plurality of batteries 1 with a common electrolyte supplydevice 21 can be supplied with the respective electrolyte flow. Inparticular, a common control device 22 can be used in order to operate aplurality of batteries 1 or the battery system 57. In particular, commonconveying devices can then also be used for producing the air flows orelectrolyte flows for the individual batteries 1. The batteries 1 can beconnected electrically in series or in parallel. Independently of thisthe electrolyte paths 17 of the batteries 1 can be arranged fluidicallyin parallel or in series. For example, a common electrolyte circuit 41can be provided in which a plurality of batteries are fluidicallyincorporated so that further components of the electrolyte circuit 41can be used jointly such as, for example, the electrolyte cleaningdevice 47 and/or the gas separating device 48. Likewise, the air paths14 of the batteries 1 can be arranged fluidically in parallel or inseries where further components of the air supply device 20 can also beused jointly here, such as, for example the concentrating device 38 oran air filter.

A vehicle which has an electric motor drive can be fitted with at leastone battery 1 of the previously described type or with the previouslydescribed battery system 57 in order to provide electrical energy forthe respective electric motor. It is of particular advantage here thatas a result of its hydraulic or hydro-pneumatic power control or powerregulation, the battery 1 presented here can be electrically connectedin principle unbuffered to the respective power consumer of the vehicleor to a corresponding power electronics so that in particular heavyrechargeable batteries and the like can be dispensed with.

For operating such a metal-air battery 1 or such a battery system 57, itcan now be provided that depending on a current power requirement forthe metal-air battery 1 or for the battery system 57 a suitableelectrolyte flow and/or a suitable air flow for the respective battery 1is/are generated. Expediently for this purpose it can be provided thatfor adapting the electrolyte flow the respective electrolyte conveyingdevice, i.e. preferably the electrolyte pumps 45, 46 or the rotatinglydriven anode 11 is actuated accordingly to increase or reduce itsconveying capacity and/or that for adapting the air flow the respectiveair conveying device, i.e. preferably the fan 40, is actuatedaccordingly to increase or reduce its conveying capacity.

The anode 11 can be produced according to FIG. 1 and according to aparticularly advantageous embodiment so that it comprises an anode body12 in a sodium matrix 53 in which particles 54 of an aluminium alloy areembedded. This therefore does not comprise an aluminium sodium alloy butan aluminium sodium composite material. This is achieved whereby agranular material comprising an aluminium alloy which forms theparticles 54 is introduced into a sodium melt which thereby forms thematrix 53. The anode 11 or the anode body 12 can be cast with the aid ofthis sodium melt which contains the particles 54 of the aluminium alloy.

The particles 54 can, for example have a particle size of 10 μm to 100μm. Preferred is a particle size of 40 μm to 60 μm. Particularlypreferred is a particle size of about 50 μm. The fraction of theparticles 54 in the anode body 12 is preferably in a range of 40% to80%. A particle fraction of 60% to 70% is advantageous. Particularlypreferred is a particle fraction of about 65%. Weight percent is meanthere.

The aluminium alloy from which the particles 54 are produced canaccording to an advantageous embodiment contain zirconium. It has beenfound that zirconium in the aluminium alloy reduces the formation of abarrier layer at the outer side 36 of the anode body 12 so far that adirect reaction of aluminium with water to form aluminium oxide andhydrogen is largely avoided. The aluminium alloy preferably contains0.01% to 1.00% zirconium. A zirconium fraction of 0.05% to 0.8% ispreferred. A zirconium fraction of about 0.5% is particularlyadvantageous. The preceding percentage details are weight percent. Thealuminium alloy exclusively consists of aluminium apart from unavoidableimpurities due to manufacture.

The electrolyte preferably used here consists of an aqueous acid or anaqueous lye to which at least one halogen and at least one surfactant isadded. Halogens are fluorine, chlorine, bromine, iodine, astatine andununseptium. Particularly fluorine, chlorine, bromine and iodine areconsidered as the electrolyte. Fluorine is preferred here. The halogensare not used in pure form but in the form of fluorine compounds, inparticular in the form of fluorine-containing salts, so-calledfluorides. Surfactants are substances which reduce the surface tensionof a liquid or the interface tension between two phases and enable orassist the formation of dispersions or act as solubilizers.

The acid or lye used for the electrolyte has a concentration of 10% to40% in water. Preferred is a concentration in the range of 15% to 25%.Particularly advantageous is a concentration of about 20%. The halogenhas a fraction of 0.1% to 4.0% inside the acid or lye. Preferred is ahalogen fraction of 0.5% to 2.0%. A preferred halogen is potassiumaluminium pentafluoride. The surfactant has a fraction of 0.1% to 2.0%in the acid or lye. A surfactant fraction of 0.2% to 1.0% is preferred.Sodium lauryl sulphate is preferred as surfactant. The precedingpercentage details should each be understood as weight percent.

The invention claimed is:
 1. An anode for an aluminium-air battery,comprising an anode body which contains particles of an aluminium alloyembedded in a sodium matrix, wherein the anode body has flow-guidingstructures configured to enable a torque to be transmitted to the anodefrom an electrolyte flow, the flow-guiding structures being in the formof screw-shaped vanes or vane sections.
 2. The anode according to claim1, wherein the particles have a particle size of 10 μm to 100 μm.
 3. Theanode according to claim 1, wherein a fraction of the particles in theanode body lies in a range of 40% to 80%, the remainder being the sodiummatrix.
 4. The anode according to claim 1, wherein the aluminium alloycontains zirconium.
 5. The anode according to claim 4, wherein thealuminium alloy contains 0.01% to 1.00% zirconium.
 6. The anodeaccording to claim 5, wherein the aluminium alloy contains 0.05% to0.80% zirconium.
 7. A method for manufacturing an anode for analuminium-air battery, comprising: embedding particles of a granularmaterial comprising an aluminium alloy into a sodium matrix; and castingan anode body of the anode comprising the sodium matrix with thegranular material, the anode body having flow-guiding structures in theform of screw-shaped vanes or vane sections, the flow-guiding structuresconfigured to enable a torque to be transmitted to the anode from anelectrolyte flow.
 8. An electrolyte for driving the anode according toclaim 1, the electrolyte consisting of an aqueous lye containing atleast one halogen and at least one surfactant.
 9. The electrolyteaccording to claim 8, wherein the aqueous lye comprises a 10% to 40%fraction in water.
 10. The electrolyte according to claim 8, wherein theat least one halogen comprises a 0.1% to 4.0% fraction in the aqueouslye.
 11. The electrolyte according to claim 10, wherein the at least onehalogen comprises a 0.5% to 2.0% fraction in the aqueous lye.
 12. Theelectrolyte according to claim 8, wherein the at least one halogen is afluoride.
 13. The electrolyte according to claim 8, wherein the at leastone surfactant comprises a fraction of 0.1% to 2.0% in the aqueous lye.14. The electrolyte according to claim 13, wherein the at least onesurfactant comprises a fraction of 0.2% to 1.0% in the aqueous lye. 15.The electrolyte according to claim 8, wherein the at least onesurfactant is sodium lauryl sulphate.
 16. A metal-air battery,comprising: a housing having an electrolyte inlet and an electrolyteoutlet; a cathode separating an air space from an electrolyte space inthe housing; an anode; an electrolyte disposed between the cathode andthe anode; wherein the anode includes an anode body which containsparticles of an aluminium embedded alloy in a sodium matrix; wherein theelectrolyte consists of one of an aqueous acid or an aqueous lyecontaining at least one halogen and at least one surfactant; and whereinthe electrolyte inlet arranged tangentially to an electrolyte space; andwherein the anode body has flow-guiding structures configured to enablea torque to be transmitted to the anode from a flow of the electrolyte,the flow-guiding structures being in the form of screw-shaped vanes orvane sections.
 17. The anode according to claim 2, wherein the particleshave a particle size of 40 μm to 60 μm.
 18. The anode according to claim3, wherein a fraction of the particles in the anode body lies in a rangeof 60% to 70%.
 19. The electrolyte according to claim 8, wherein the atleast one halogen is potassium aluminium pentafluoride.
 20. Theelectrolyte according to claim 9, wherein the at least one halogencomprises a 0.1% to 4.0% fraction in the aqueous lye.